1. Field of the Invention
The present invention relates to an arrangement for introducing audio-frequency signals into a power supply line containing a compensating capacitor, through a junction converter having a primary winding which is connected with an audio-frequency signal generator.
2. Discussion of the Prior Art
In the power supply lines there is frequently effected a command or information transmission with the assistance of signals which are superimposed on the supply voltage. The frequency of these signals usually lies within the audiofrequency range of between 150 Hz and 20 kHz and, consequently, they are also designated as audio-frequency signals. The introduction of these audio-frequency signals is usually effected through a junction converter whose primary winding is connected with an audio-frequency signal generator and whose secondary winding is connected between two phases. However, hereby it must be noted that the capacitors which are occasionally present in the power supply will impart a load on the audio-frequency signal. For example, median-voltage supply lines are frequency compensated by means of star-connected compensating capacitors. These compensating capacitors evidence a relatively high capacitance. These compensating condensers represent an impedance to the audio-frequency signals, which is lower at the higher frequencies and vise versa of the audiofrequency signals. The compensating capacitors thereby represent a high loading on the audio-frequency generator which, above all, corresponds to a short-circuit in the upper frequency range of the audio frequency signals. At higher frequencies, for the introduction of the audio-frequency signals without the application of additional measures, there is required an uneconomically high level of transmitting power. Moreover, the audio-frequency signals represent an additional load on the compensating capacitors. In current installations, an inductive impedance is connected ahead of each capacitor. As a result thereof, there is increased the impedance which is effective for the audi-frequency signals; in essence, there is reduced the load on the audio-frequency signal generator. Since impedances of that type must be designed for the full current which flows through the capacitor, they become quite large and are installed with difficulty.